DESCRIPTION

vm_page_bits() calculates the bits representing the DEV_BSIZE range of
bytes between base and size. The byte range is expected to be within a
single page, and if size is zero, no bits will be set.
vm_page_set_validclean() flags the byte range between base and size as
valid and clean. The range is expected to be DEV_BSIZE aligned and no
larger than PAGE_SIZE. If it is not properly aligned, any unaligned
chucks of the DEV_BSIZE blocks at the beginning and end of the range will
be zeroed.
If base is zero and size is one page, the modified bit in the page map is
cleared; as well, the PG_NOSYNC flag is cleared.
vm_page_clear_dirty() clears the dirty bits within a page in the range
between base and size. The bits representing the range are calculated by
calling vm_page_bits().
vm_page_set_invalid() clears the bits in both the valid and dirty flags
representing the DEV_BSIZE blocks between base and size in the page. The
bits are calculated by calling vm_page_bits(). As well as clearing the
bits within the page, the generation number within the object holding the
page is incremented.
vm_page_zero_invalid() zeroes all of the blocks within the page that are
currently flagged as invalid. If setvalid is TRUE, all of the valid bits
within the page are set.
In some cases, such as NFS, the valid bits cannot be set in order to
maintain cache consistency.
vm_page_is_valid() checks to determine if the all of the DEV_BSIZE blocks
between base and size of the page are valid. If size is zero and the
page is entirely invalid vm_page_is_valid() will return TRUE, in all
other cases a size of zero will return FALSE.
vm_page_test_dirty() checks if a page has been modified via any of its
physical maps, and if so, flags the entire page as dirty.
vm_page_dirty() is called to modify the dirty bits.
vm_page_dirty() flags the entire page as dirty. It is expected that the
page is not currently on the cache queue.
vm_page_undirty() clears all of the dirty bits in a page.